This invention relates to a DC motor drive system, and more particularly to a DC motor drive system which is adapted to prevent spark generation of the brush portion resulting from an increase in a load and which is of particular utility when employed for driving a DC motor of the type using a permanent magent.
In a DC motor, when the motor output exceeds a certain value with an increase in a load, the brush portion produces sparking. The spark generation of the brush decreases the lifetime of the motor and in its turn leads to breakage of the motor.
It is one object of this invention to provide a DC motor drive system which controls the motor speed so that the motor output may not exceed a predetermined value.
It is another object of this invention to provide a DC motor drive system which controls the motor speed to hold the motor output less than a predetermined value, preventing spark generation of the brush portion for the protection of the motor.
The above objects are achieved by providing a DC motor drive system which has means for detecting the power of a DC motor and feedback means for changing the motor speed in response to the detected power and wherein the motor speed is changed so that the power does not exceed the allowed value of the motor.